Working in the American automotive and aerospace industries for decades, the authors identified a problem with the fastener-joints to be solved, and this prompted them into this innovation process.
The fasteners most commonly used in various industries (automotive, aerospace etc.) do not provide adequate torque and self-locking features to resist loss of preload or axial tension under dynamic/vibratory loading.
Few predecessors tried to incorporate various features to add self-locking capabilities to the joints. In particular, Nylok and Longlok fasteners that are already in use provide torque that is suitable up to moderate temperature (250° F.) applications. Another group of fasteners called Dyna-thread II was designed such that the periphery of its controlled thread area is dilated to produce the desired torque. Even though it can be used as a high temperature application, there is a limitation on the size of the bolt itself (1″ O.D./nominal size max.). Additionally, on such fasteners, it becomes difficult to control the expansion of threaded area as the nominal diameter of the bolt increases. Furthermore, as such engineering applications may need higher torque, one may need to increase the dilation of the thread but that in turn gets cumbersome as the bolt diameter increase (1″ O.D./nominal size max.).
In addition to the above concerns, dilated fasteners experience lower strength capabilities (due to a very thin wall) on the dilated surface compared to the rated strength capabilities at the full cross section of the fastener. Lastly, under mechanical loading, such dilations could lead to a shear failure due to a reduced load transfer or result in a fatigue failure of the fastener due to repeated loading and unloading.